Presently known submersible motors are submerged motors which utilize a filling fluid of either an oil or water type mixture to satisfy a number of functions including dielectric insulation, bearing lubrication, heat transfer and pressure transmission.
The conventional fluids have a number of disadvantages especially at higher temperatures (150.degree. F. and above). Water or water-glycerine mixtures, in particular, exhibit very poor lubricating properties and liberate entrained gasses. Also, they boil as higher temperatures are encountered. Oils offer the advantages of good dielectric properties, higher gassing and boiling points and better lubricating characteristics, but do not equal the properties of water such as heat transfer, low thermal expansion rate or viscosity/pressure characteristics. They also require substantial sealing means to prevent the ingress of the process fluid in which the machine is submerged.